This invention relates to a method for the management of low level radioactive nuclear power plant wastes, in particular the compaction and disposal of beadand powdered ion exchange resins mixed with a filter aid.
One of the common low-level radioactive waste products produced by nuclear power plants is ion exchange resins. These resins are used to process water that circulates through the core of the nuclear reactor or steam generator. While ion exchange resin remove ion contaminants from plant coolant water, the filter aid removes undissolved particulates. A filter aid is any material such as cellulose layered on a filter cartridge along with the powdered resin to remove solid material. The resin and filter aid do not chemically react at the water temperature encountered in processing water from the nuclear plant, usually below about 60.degree. C. Elevated temperatures, those much above about 60.degree. C., are not usual and water of 100.degree. C. or greater is not encountered because the processing system is not pressurized.
Bead type resins are usually used in pressurized water reactor type plants to remove ions, but are not mixed with a filter aid since filtration is not intended. Boiling water reactor type plants use the powered resin with cellulose filter aid for the dual purpose of ion exchange and filtration. The resins, and cellulose when spent retain residual radioactivity and have to be disposed of in a safe manner which usually requires burial in a land fill.
The current practice is to encapsulate the resin in a matrix of cement or polymer to ensure adequate mechanical integrity as well as preventing leaching of radioactive substances from the resin by ground water. The disadvantage of this method is that it increases the volume of material that needs to be disposed. The price of disposal is closely related to the volume of material. Another method recently developed uses high integrity containers to hold the resins and cellulose without the addition of cement. The containers are designed to maintain boundary integrity for several hundred years. But again, the cost of transporting and burying the wastes is based upon their volume. Significant cost savings can be realized if the volumes are reduced.
It is the object of this invention, therefore, to describe a method whereby the volume of ion exchange resins mixed with filter aid can be significantly reduced, and it is a further object of this invention to describe a method wherein the volume reduced resins display the ability to resist dissolution of the radioactive material in the presence of water.